Just noticed, you can now also add an Exclusion Script directly in the Send Email modal dialog within Journey Builder on Step 2. But if you added it using the steps provided above, you will see it in this modal anyway.
– Eliot HarperOct 12 '16 at 3:33

@EliotHarper: Just for clarification, will the above step not mean that the contact will not receive the mail itself if it falls on Saturday and is moved to the next step in JB without getting mail. This solution will not hold good if someone want the contact to wait till Monday for the next mail to go out from JB
– Ganesh KumarOct 18 '16 at 8:48

Yes, that's correct, it will skip sending the email and the Contact will progress onto the next activity in the Journey.
– Eliot HarperOct 18 '16 at 20:02

Is there a solution that would delay the send like GaneshKumar was asking about in the above comment? @EliotHarper
– Tom CallahanOct 20 '17 at 17:54

If you are using Automation studio or event automation to fire your journey builder, there is no option to specify black out periods.

However, Automation studio and Event automation has a specific feature - Repeat on Weekdays which would suffice your requirement to inject contacts into a journey builder only on working days (Mon- Fri)

If you are using Triggered event to trigger journey builder, suggest you handle it at the trigger side to control the journey builder entry.

If you're using an Automation or an Automation to Trigger a Journey, you can also write some SQL Script to determine the day of week or hour of day and based on that (a) cause no one to be eligible or (b) cause the Automation to end.